The field of the invention relates to engine airflow and torque control in internal combustion engines.
In some engines, an electronically controlled throttle is used for improved performance. In particular, the electronic throttle is used to control airflow to a desired value determined from operating conditions and an operator command. In this way, the vehicle can achieve improved drive feel and improved fuel economy.
In this system, the required airflow is used to determine an initial setting of the throttle. Also, a difference between required airflow and actual measured airflow is used to adjust the initial setting of the throttle. Thus, the throttle is used to control airflow and thereby engine torque. Such a system is described in U.S. Pat. No. 5,019,989.
The inventors herein have recognized a disadvantage with the above approach. In particular, a disadvantage with using throttle position is that the throttle cannot quickly change engine torque since the throttle controls flow entering an intake manifold. Controlling flow entering the manifold cannot rapidly control cylinder charge due to manifold volume. For example, if the throttle is instantly closed, cylinder air charge does not instantly decrease to zero. The engine must pump down the air stored in the manifold, which takes a certain number of revolutions. Therefore, the cylinder air charge gradually decreases toward zero.
Also, other methods are known for controlling engine torque where ignition timing is used. In particular, to maximize fuel economy, ignition timing should be at MBT timing (ignition timing for maximum torque). However, when at this point, adjustment of ignition timing in any direction decreases engine torque and fuel economy. Therefore, when maximizing fuel economy, engine torque can be rapidly increased. To be able to use ignition timing in both positive and negative directions, ignition timing must be set away from MBT timing. This allows rapid engine torque control, but at the cost of degraded fuel economy.
An object of the present invention is to rapidly control engine airflow.
The above object is achieved and disadvantages of prior approaches overcome by a method for controlling an engine airflow, the engine having at least one cylinder, the engine also having an intake manifold and an outlet control device for controlling flow from the intake manifold into the cylinder, comprising: generating a desired flow into the cylinder; and adjusting the outlet control device to provide said desired flow into the cylinder.
By using an outlet control device that controls flow exiting the manifold (entering the cylinder), it is possible to rapidly change engine airflow, despite response delays of airflow inducted through the intake manifold. Further, by responding to a request for flow entering the cylinder, more accurate and rapid control can be achieved. In other words, a rapid change in cylinder charge can be achieved, thereby providing a rapid change in engine torque.
An advantage of the above aspect of the invention is faster airflow and cylinder air charge control.
Another advantage of the above aspect of the invention is that manifold volume does not limit the maximum rate of change of engine airflow.
In another aspect of the present invention, the above object is achieved, and disadvantages of prior approaches overcome by a method for controlling an engine airflow, the engine having at least one cylinder, the engine also having an intake manifold and an outlet control device for controlling flow from the intake manifold into the cylinder and an inlet control device for controlling flow into the intake manifold, comprising: generating a desired cylinder air amount; and adjusting both the inlet control device and the outlet control device to provide said desired cylinder air amount.
By changing both the inlet and outlet control devices, it is possible to rapidly change engine airflow and cylinder air charge despite response delays of airflow inducted through the intake manifold. In other words, the present invention controls manifold inlet and outlet flows in a coordinated way to allow a rapid change in cylinder air charge regardless of manifold volume.
An advantage of the above aspect of the invention is that by using both an outlet and an inlet control device, a more controlled rapid change in engine airflow can be achieved.
In yet another aspect of the present invention, the above object is achieved and disadvantages of prior approaches overcome by a method for controlling an engine airflow, the engine having at least one cylinder, the engine also having an intake manifold and an outlet control device for controlling flow from the intake manifold into the cylinder, comprising: generating a desired engine torque; generating a desired cylinder air charge amount based on said desired engine torque; and changing the outlet control device to provide said desired cylinder air charge amount and thereby provide said desired engine torque.
In still another aspect, the present invention comprises a method for controlling an engine airflow, the engine having at least one cylinder, the engine also having an intake manifold and an outlet control device for controlling flow from the intake manifold into the cylinder, comprising: generating a desired change of engine torque; generating a desired cylinder air charge amount based on said desired change of engine torque; and changing the outlet control device to provide said desired cylinder air charge amount and thereby cause a change of engine torque.
By changing both the inlet and outlet control devices, it is possible to rapidly change engine torque despite response delays of airflow inducted through the intake manifold.
An advantage of the above aspect of the invention is that rapid engine torque control can be achieved without degraded fuel economy.
Another advantage of the present invention is improved fuel economy.
Other objects, features and advantages of the present invention will be readily appreciated by the reader of this specification.